This work is designed to elucidate some of the factors which regulate removal of neutral lipid from the circulation. Triglyceride transport from the circulation to adipose tissue depends on hydrolysis of lipoprotein bound triglyceride by lipoprotein lipase. Lipoprotein lipase, in turn, may be regulated by a factor in serum which enhances lipoprotein lipase release from fat cells in vitro. We plan to develop immunoassays for lipoprotein lipase and for lipoprotein lipase releasing factor of serum. Such assays will allow measurement of precursor, inactive, and defective proteins, Antisera will be used to localize lipoprotein lipase and releasing factor in tissue at the light and electron microscopic levels. We will determine whether any morphologic changes in adipocytes occur as a consequence of exposure of these cells to lipoprotein lipase releasing factor. The role of lipoprotein lipase and the lipoprotein lipase releasing factor in lipid transport will be studied by determining the effects of nutritional, hormonal, and metabolic states on their activities. These activities will be correlated with plasma triglyceride concentrations especially in hyperlipemic subjects. Methods already employed successfully in studying lipoprotein lipase from animal tissues and methods already used for isolation and immuno-chemical characterization of lipoproteins will be used. BIBLIOGRAPHIC REFERENCES: Nilsson-Ehle, P., Garfinkel, A.S., and Schotz, M.C. Effects of platelets on lipoprotein lipase activity. Life Sciences 16: (1975) 1703-1710. Twu, J.S., Garfinkel, A.S., and Schotz, M.C. Rat heart lipoprotein lipase. Atherosclerosis. 22: (1975) 463-472.